The weather forecast is for sun, with intermittent showers.
I gather it wants to say "the weather forecast tells people it's sunny with intermittent showers". But I couldn't understand this part "for sun". I guess 'sun' is the written abbreviation of 'sunny'(though I didn't find this usage in the dictionary). Even if so, what's the meaning of "for" here? Does it mean something like "support"? That's the only meaning I could imagine, though it's weird.
How to explain this part "for sun"?